Supplementation of lactating ewes with a glucogenic preparation or β-carotene in mid- to late lactation, on subsequent milk yield and luteinizing hormone secretion

Abstract

The effects of a glucogenic preparation (Nutrimix®) or β-carotene (Rovimix® beta carotene) supplementation of ewes during mid- to late-lactation on their milk yield were assessed in a study where 66 Chios-breed ewes were allocated into three equal (n = 22) groups. Ewes in group A received daily a glucogenic preparation and those in group B β-carotene, starting 35 d before estrus synchronization until 7 d after artificial insemination (supplementation period); ewes in group C were untreated controls. The estrus cycle was synchronized and double AI was carried out 48 and 60 h after withdrawal of progestagen sponges. Milk yield was measured daily during the supplementation period. Blood samples were collected at 2-h intervals, from 28 to 54 h after sponge withdrawal; the concentration of plasma luteinizing hormone (LH) was measured. Increased milk yield was recorded after supplementation with the glucogenic preparation (P < 0.05), but not with β-carotene (P > 0.05). There were no differences in LH concentration during surge release in supplemented ewes; furthermore, there were no differences between groups in body weight and litter size. It is concluded that supplementation of ewes with a glucogenic preparation during mid- to late-lactation may lead to improved milk production. Key words: Sheep reproduction, milk yield, β-carotene, energy, luteinizing hormone